CHANGES IN COMMON STOCK (Details) - USD ($) $ / shares in Units, $ in Millions	2 Months Ended	4 Months Ended	6 Months Ended
	Jun. 30, 2018	Apr. 30, 2018	Jun. 30, 2018	Jun. 30, 2017
Number of common shares outstanding
Balance, beginning of year (in shares)		166,857,931	166,857,931
Balance, end of year (in shares)	164,433,085		164,433,085
Number of stock tendered for payment of federal and state taxes owed (in shares)			235,000
Stock repurchased and retired during period, value			$ 60.5	$ 111.9
Stock repurchase program, remaining repurchase authorized amount	$ 325.1		325.1
Common stock dividends declared			$ 32.0	29.4
Dividends (in dollars per share)	$ 0.10	$ 0.09	$ 0.19
Common stock and additional paid-in capital
Number of common shares outstanding
Stock repurchased and retired during period, value			$ 60.5	$ 111.9
Common stock
Number of common shares outstanding
Balance, beginning of year (in shares)		166,858,000	166,858,000
Stock repurchased and retired during period, shares			(2,998,000)
Balance, end of year (in shares)	164,433,000		164,433,000
Common stock | Stock options
Number of common shares outstanding
Shares issued under employee benefit compensation plans (in shares)			132,000
Number of stock tendered for payment of federal and state taxes owed (in shares)			69,000
Common stock | Restricted and Performance Stock
Number of common shares outstanding
Shares issued under employee benefit compensation plans (in shares)			441,000